/*
 * module for openGauss to access client SSL certificate information
 *
 * Written by Victor B. Wagner <vitus@cryptocom.ru>, Cryptocom LTD
 * This file is distributed under BSD-style license.
 *
 * contrib/sslinfo/sslinfo.c
 */

#include "postgres.h"
#include "knl/knl_variable.h"
#include "fmgr.h"
#include "utils/numeric.h"
#include "utils/numeric_gs.h"
#include "libpq/libpq-be.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "mb/pg_wchar.h"

#include <openssl/x509.h>
#include <openssl/asn1.h>

PG_MODULE_MAGIC;

Datum ssl_is_used(PG_FUNCTION_ARGS);
Datum ssl_version(PG_FUNCTION_ARGS);
Datum ssl_cipher(PG_FUNCTION_ARGS);
Datum ssl_client_cert_present(PG_FUNCTION_ARGS);
Datum ssl_client_serial(PG_FUNCTION_ARGS);
Datum ssl_client_dn_field(PG_FUNCTION_ARGS);
Datum ssl_issuer_field(PG_FUNCTION_ARGS);
Datum ssl_client_dn(PG_FUNCTION_ARGS);
Datum ssl_issuer_dn(PG_FUNCTION_ARGS);
Datum X509_NAME_field_to_text(X509_NAME* name, text* fieldName);
Datum X509_NAME_to_text(X509_NAME* name);
Datum ASN1_STRING_to_text(ASN1_STRING* str);

/*
 * Indicates whether current session uses SSL
 *
 * Function has no arguments.  Returns bool.  True if current session
 * is SSL session and false if it is local or non-ssl session.
 */
PG_FUNCTION_INFO_V1(ssl_is_used);
Datum ssl_is_used(PG_FUNCTION_ARGS)
{
    PG_RETURN_BOOL(u_sess->proc_cxt.MyProcPort->ssl != NULL);
}

/*
 * Returns SSL cipher currently in use.
 */
PG_FUNCTION_INFO_V1(ssl_version);
Datum ssl_version(PG_FUNCTION_ARGS)
{
    if (u_sess->proc_cxt.MyProcPort->ssl == NULL)
        PG_RETURN_NULL();
    PG_RETURN_TEXT_P(cstring_to_text(SSL_get_version(u_sess->proc_cxt.MyProcPort->ssl)));
}

/*
 * Returns SSL cipher currently in use.
 */
PG_FUNCTION_INFO_V1(ssl_cipher);
Datum ssl_cipher(PG_FUNCTION_ARGS)
{
    if (u_sess->proc_cxt.MyProcPort->ssl == NULL)
        PG_RETURN_NULL();
    PG_RETURN_TEXT_P(cstring_to_text(SSL_get_cipher(u_sess->proc_cxt.MyProcPort->ssl)));
}

/*
 * Indicates whether current client have provided a certificate
 *
 * Function has no arguments.  Returns bool.  True if current session
 * is SSL session and client certificate is verified, otherwise false.
 */
PG_FUNCTION_INFO_V1(ssl_client_cert_present);
Datum ssl_client_cert_present(PG_FUNCTION_ARGS)
{
    PG_RETURN_BOOL(u_sess->proc_cxt.MyProcPort->peer != NULL);
}

/*
 * Returns serial number of certificate used to establish current
 * session
 *
 * Function has no arguments.  It returns the certificate serial
 * number as numeric or null if current session doesn't use SSL or if
 * SSL connection is established without sending client certificate.
 */
PG_FUNCTION_INFO_V1(ssl_client_serial);
Datum ssl_client_serial(PG_FUNCTION_ARGS)
{
    Datum result;
    Port* port = u_sess->proc_cxt.MyProcPort;
    X509* peer = port->peer;
    ASN1_INTEGER* serial = NULL;
    BIGNUM* b = NULL;
    char* decimal = NULL;

    if (!peer)
        PG_RETURN_NULL();
    serial = X509_get_serialNumber(peer);
    b = ASN1_INTEGER_to_BN(serial, NULL);
    decimal = BN_bn2dec(b);

    BN_free(b);
    result = DirectFunctionCall3(numeric_in, CStringGetDatum(decimal), ObjectIdGetDatum(0), Int32GetDatum(-1));
    OPENSSL_free(decimal);
    return result;
}

/*
 * Converts OpenSSL ASN1_STRING structure into text
 *
 * Converts ASN1_STRING into text, converting all the characters into
 * current database encoding if possible.  Any invalid characters are
 * replaced by question marks.
 *
 * Parameter: str - OpenSSL ASN1_STRING structure.	Memory management
 * of this structure is responsibility of caller.
 *
 * Returns Datum, which can be directly returned from a C language SQL
 * function.
 */
Datum ASN1_STRING_to_text(ASN1_STRING* str)
{
    BIO* membuf = NULL;
    size_t size;
    char nullterm;
    char* sp = NULL;
    char* dp = NULL;
    text* result = NULL;

    membuf = BIO_new(BIO_s_mem());
    (void)BIO_set_close(membuf, BIO_CLOSE);
    ASN1_STRING_print_ex(membuf, str, ((ASN1_STRFLGS_RFC2253 & ~ASN1_STRFLGS_ESC_MSB) | ASN1_STRFLGS_UTF8_CONVERT));
    /* ensure null termination of the BIO's content */
    nullterm = '\0';
    BIO_write(membuf, &nullterm, 1);
    size = BIO_get_mem_data(membuf, &sp);
    dp = (char*)pg_do_encoding_conversion((unsigned char*)sp, size - 1, PG_UTF8, GetDatabaseEncoding());
    result = cstring_to_text(dp);
    if (dp != sp)
        pfree(dp);
    BIO_free(membuf);

    PG_RETURN_TEXT_P(result);
}

/*
 * Returns specified field of specified X509_NAME structure
 *
 * Common part of ssl_client_dn and ssl_issuer_dn functions.
 *
 * Parameter: X509_NAME *name - either subject or issuer of certificate
 * Parameter: text fieldName  - field name string like 'CN' or commonName
 *			  to be looked up in the OpenSSL ASN1 OID database
 *
 * Returns result of ASN1_STRING_to_text applied to appropriate
 * part of name
 */
Datum X509_NAME_field_to_text(X509_NAME* name, text* fieldName)
{
    char* string_fieldname = NULL;
    int nid, index;
    ASN1_STRING* data = NULL;

    string_fieldname = text_to_cstring(fieldName);
    nid = OBJ_txt2nid(string_fieldname);
    if (nid == NID_undef)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("invalid X.509 field name: \"%s\"", string_fieldname)));
    pfree(string_fieldname);
    index = X509_NAME_get_index_by_NID(name, nid, -1);
    if (index < 0)
        return (Datum)0;
    data = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(name, index));
    return ASN1_STRING_to_text(data);
}

/*
 * Returns specified field of client certificate distinguished name
 *
 * Receives field name (like 'commonName' and 'emailAddress') and
 * returns appropriate part of certificate subject converted into
 * database encoding.
 *
 * Parameter: fieldname text - will be looked up in OpenSSL object
 * identifier database
 *
 * Returns text string with appropriate value.
 *
 * Throws an error if argument cannot be converted into ASN1 OID by
 * OpenSSL.  Returns null if no client certificate is present, or if
 * there is no field with such name in the certificate.
 */
PG_FUNCTION_INFO_V1(ssl_client_dn_field);
Datum ssl_client_dn_field(PG_FUNCTION_ARGS)
{
    text* fieldname = PG_GETARG_TEXT_P(0);
    Datum result;

    if (!(u_sess->proc_cxt.MyProcPort->peer))
        PG_RETURN_NULL();

    result = X509_NAME_field_to_text(X509_get_subject_name(u_sess->proc_cxt.MyProcPort->peer), fieldname);

    if (!result)
        PG_RETURN_NULL();
    else
        return result;
}

/*
 * Returns specified field of client certificate issuer name
 *
 * Receives field name (like 'commonName' and 'emailAddress') and
 * returns appropriate part of certificate subject converted into
 * database encoding.
 *
 * Parameter: fieldname text - would be looked up in OpenSSL object
 * identifier database
 *
 * Returns text string with appropriate value.
 *
 * Throws an error if argument cannot be converted into ASN1 OID by
 * OpenSSL.  Returns null if no client certificate is present, or if
 * there is no field with such name in the certificate.
 */
PG_FUNCTION_INFO_V1(ssl_issuer_field);
Datum ssl_issuer_field(PG_FUNCTION_ARGS)
{
    text* fieldname = PG_GETARG_TEXT_P(0);
    Datum result;

    if (!(u_sess->proc_cxt.MyProcPort->peer))
        PG_RETURN_NULL();

    result = X509_NAME_field_to_text(X509_get_issuer_name(u_sess->proc_cxt.MyProcPort->peer), fieldname);

    if (!result)
        PG_RETURN_NULL();
    else
        return result;
}

/*
 * Equivalent of X509_NAME_oneline that respects encoding
 *
 * This function converts X509_NAME structure to the text variable
 * converting all textual data into current database encoding.
 *
 * Parameter: X509_NAME *name X509_NAME structure to be converted
 *
 * Returns: text datum which contains string representation of
 * X509_NAME
 */
Datum X509_NAME_to_text(X509_NAME* name)
{
    BIO* membuf = BIO_new(BIO_s_mem());
    int i, nid, count = X509_NAME_entry_count(name);
    X509_NAME_ENTRY* e = NULL;
    ASN1_STRING* v = NULL;
    const char* field_name = NULL;
    size_t size;
    char nullterm;
    char* sp = NULL;
    char* dp = NULL;
    text* result = NULL;

    (void)BIO_set_close(membuf, BIO_CLOSE);
    for (i = 0; i < count; i++) {
        e = X509_NAME_get_entry(name, i);
        nid = OBJ_obj2nid(X509_NAME_ENTRY_get_object(e));
        v = X509_NAME_ENTRY_get_data(e);
        field_name = OBJ_nid2sn(nid);
        if (!field_name)
            field_name = OBJ_nid2ln(nid);
        BIO_printf(membuf, "/%s=", field_name);
        ASN1_STRING_print_ex(membuf, v, ((ASN1_STRFLGS_RFC2253 & ~ASN1_STRFLGS_ESC_MSB) | ASN1_STRFLGS_UTF8_CONVERT));
    }

    /* ensure null termination of the BIO's content */
    nullterm = '\0';
    BIO_write(membuf, &nullterm, 1);
    size = BIO_get_mem_data(membuf, &sp);
    dp = (char*)pg_do_encoding_conversion((unsigned char*)sp, size - 1, PG_UTF8, GetDatabaseEncoding());
    result = cstring_to_text(dp);
    if (dp != sp)
        pfree(dp);
    BIO_free(membuf);

    PG_RETURN_TEXT_P(result);
}

/*
 * Returns current client certificate subject as one string
 *
 * This function returns distinguished name (subject) of the client
 * certificate used in the current SSL connection, converting it into
 * the current database encoding.
 *
 * Returns text datum.
 */
PG_FUNCTION_INFO_V1(ssl_client_dn);
Datum ssl_client_dn(PG_FUNCTION_ARGS)
{
    if (!(u_sess->proc_cxt.MyProcPort->peer))
        PG_RETURN_NULL();
    return X509_NAME_to_text(X509_get_subject_name(u_sess->proc_cxt.MyProcPort->peer));
}

/*
 * Returns current client certificate issuer as one string
 *
 * This function returns issuer's distinguished name of the client
 * certificate used in the current SSL connection, converting it into
 * the current database encoding.
 *
 * Returns text datum.
 */
PG_FUNCTION_INFO_V1(ssl_issuer_dn);
Datum ssl_issuer_dn(PG_FUNCTION_ARGS)
{
    if (!(u_sess->proc_cxt.MyProcPort->peer))
        PG_RETURN_NULL();
    return X509_NAME_to_text(X509_get_issuer_name(u_sess->proc_cxt.MyProcPort->peer));
}
